Sundarbans - the wonders of worldPosted by Nikkon on October 7th, 2010 The Sundarbans, covering some 10,000 square kilometers (sq.km) of land and water, is part of the world's largest delta (80,000sq.km) formed from sediments deposited by three great rivers, the Ganges, Brahmaputra and Meghna, which converge on the Bengal Basin. The total area of the Bangladesh Sundarbans is 5,771sq.km (almost 62 percent of the total), of which 4,071sq.km is land and the rest water. This area is approximately half the size of the area of mangrove that existed 200 years ago, the other half being cleared and converted to agricultural land. The land is molded by tidal action, resulting in a distinctive physiography. An intricate network of interconnecting waterways, of which the larger channels of often a mile or more in width run in a generally north-south direction, intersects the whole area. Innumerable small khals drain the land at each ebb. Rivers tend to be long and straight, a consequence of the strong tidal forces and the clay and silt deposits which resist erosion. Easily eroded sands collect at the river mouths and form banks and chars, which are blown into dunes above the high-water mark by the strong south-west monsoon. Finer silts are washed out into the Bay of Bengal but, where they are protected from wave action, mud flats form in the lee of the dunes. These become overlain with sand from the dunes, and develop into grassy middens. This process of island building continues for as long as the area on the windward side is exposed to wave action. With the formation of the next island further out, silt begins to accumulate along the shore of the island and sand is blown or washed away. Apart from Baleswar River the waterways carry little freshwater as they are cut off from the Ganges, the outflow of which has shifted from the Hooghly-Bhagirathi channels in India progressively eastwards since the 17th century. They are kept open largely by the diurnal tidal flow. Alluvial deposits are geologically very recent and deep. The soil is a silty clay loam with alternate layers of clay, silt and sand. The surface is clay except on the seaward side of islands in the coastal limits, where sandy beaches occur. In the eastern part of the Sundarbans the surface soil is soft and fertile, whereas it is harder and less suitable for tree growth in the west . The potential of hydrogen (pH) averages 8.0.Like it? Share it! More by this author |